I think this is very local. Here in Sweden I have only ever met one person who used Whatsapp. I feel most people use Facebook messenger with some use of Skype, Google Hangouts, Telegram, Signal and Slack.
Do telcos in US/Europe create the same incumbency that telcos in Latin America create?
Here in Mexico, any mobile data package comes with free data for blessed services like Whatsapp and FB Messenger. Obviously trying to compete with each other on these perks.
Using a competitor like Telegram is a complete nonstarter when trading memes or video chat eats into your data. The cheapest plan from Telcel (pay-as-you-go + holding 20 pesos in your balance) lets you use Whatsapp infinitely.
In Sweden they do not do that for messenger clients but they do it for video streaming sites. Data is so cheap here that a messenger would not be a good selling point.
It is probably illegal (on the paper we have net neutrality, the telcos just blatantly break the law) to do so in Sweden which why some telcos are in a legal battle with our regulatory authority.
It’s not illegal if you get user consent. I signed up (in Sweden) for a mobile contract with free Apple Music data last year, and they made a big thing of getting consent for them to do DPI to get that.
It’s actually somewhat of a grey area due to net neutrality regulations. Those are EU-wide, but up to the local regulation authority to interpret, which means that a regulator in Portugal or Sweden says it’s cool, in The Netherlands that any music service (sadly not your own Plex) can apply to be delimited, and in yet another EU country it might be completely illegal.